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Mount Prospect, Illinois 7 Day Weather Forecast
Wx Forecast - Wx Discussion - Wx Aviation
NWS Forecast for Mount Prospect IL
National Weather Service Forecast for: Mount Prospect IL
Issued by: National Weather Service Chicago, IL
Updated: 4:06 pm CDT May 21, 2026
 
Tonight

Tonight: Mostly cloudy, with a low around 49. East northeast wind 10 to 15 mph.
Mostly Cloudy

Friday

Friday: Mostly cloudy, with a high near 66. East northeast wind around 15 mph, with gusts as high as 25 mph.
Mostly Cloudy

Friday
Night
Friday Night: A 30 percent chance of showers, mainly after 4am.  Cloudy, with a low around 52. East northeast wind 10 to 15 mph, with gusts as high as 20 mph.
Chance
Showers

Saturday

Saturday: A 30 percent chance of showers, mainly before 10am.  Mostly cloudy, with a high near 70. North northeast wind 5 to 10 mph.
Chance
Showers

Saturday
Night
Saturday Night: A 20 percent chance of showers after 1am.  Mostly cloudy, with a low around 54. Northeast wind around 5 mph becoming calm  in the evening.
Mostly Cloudy
then Slight
Chance
Showers
Sunday

Sunday: A chance of showers and thunderstorms before 4pm, then a slight chance of showers.  Mostly cloudy, with a high near 78. Chance of precipitation is 30%.
Chance
Showers

Sunday
Night
Sunday Night: Mostly cloudy, with a low around 56.
Mostly Cloudy

Memorial
Day
Memorial Day: Mostly sunny, with a high near 82.
Mostly Sunny

Monday
Night
Monday Night: Partly cloudy, with a low around 59.
Partly Cloudy

Lo 49 °F Hi 66 °F Lo 52 °F Hi 70 °F Lo 54 °F Hi 78 °F Lo 56 °F Hi 82 °F Lo 59 °F

Beach Hazards Statement
Hazardous Weather Outlook
 

Tonight
 
Mostly cloudy, with a low around 49. East northeast wind 10 to 15 mph.
Friday
 
Mostly cloudy, with a high near 66. East northeast wind around 15 mph, with gusts as high as 25 mph.
Friday Night
 
A 30 percent chance of showers, mainly after 4am. Cloudy, with a low around 52. East northeast wind 10 to 15 mph, with gusts as high as 20 mph.
Saturday
 
A 30 percent chance of showers, mainly before 10am. Mostly cloudy, with a high near 70. North northeast wind 5 to 10 mph.
Saturday Night
 
A 20 percent chance of showers after 1am. Mostly cloudy, with a low around 54. Northeast wind around 5 mph becoming calm in the evening.
Sunday
 
A chance of showers and thunderstorms before 4pm, then a slight chance of showers. Mostly cloudy, with a high near 78. Chance of precipitation is 30%.
Sunday Night
 
Mostly cloudy, with a low around 56.
Memorial Day
 
Mostly sunny, with a high near 82.
Monday Night
 
Partly cloudy, with a low around 59.
Tuesday
 
Mostly sunny, with a high near 85.
Tuesday Night
 
A chance of showers. Mostly cloudy, with a low around 61.
Wednesday
 
A chance of showers. Partly sunny, with a high near 82.
Wednesday Night
 
A chance of showers. Mostly cloudy, with a low around 61.
Thursday
 
Mostly sunny, with a high near 83.

 

Forecast from NOAA-NWS for Mount Prospect IL.

Weather Forecast Discussion
178
FXUS63 KLOT 212312
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
612 PM CDT Thu May 21 2026

.KEY MESSAGES...

- Expect plenty of dry hours through Memorial Day Weekend.
  Isolated to widely scattered thunderstorms are possible late
  Saturday night into Sunday, potentially focusing primarily
  southeast of I-55 Sunday afternoon.

- Below average temperatures to close out the work week will
  trend to near to above average into next week, though notably
  cooler conditions will prevail near Lake Michigan.

&&

.DISCUSSION...
Issued at 240 PM CDT Thu May 21 2026

Through Saturday:

Seasonably strong surface high pressure centered over eastern
Canada will keep fairly status quo weather conditions, with
at times gusty northeast/east-northeast winds (strongest near
the lake) easing some tonight and then picking back up on
Friday. Extensive mid to high level cloud cover through Friday
will result in early Friday morning lows not quite as cool as
this morning (Thursday morning) but then only mid 60s to low 70s
highs inland Friday afternoon, perhaps approaching 60 lakeside.
Can`t rule out a few sprinkles out of the mid deck across
portions of far northern Illinois early to mid Friday morning as
a weak impulse passes by.

A fairly complex mid and upper level pattern will unfold Friday
afternoon into Saturday morning, with two main short-waves of
note. The first is a robust neutral to negatively tilted impulse
pivoting from the northern Plains to the central Canadian
Prairies. Our main short-wave of interest is a positively tilted
southern stream impulse (and weak surface low pressure reflection)
moving from the lower MS Valley to the central Great Lakes.

The existing dry sub-cloud layer air due to surface high
pressure influence may be tough to erode, especially with north
and northwestward extent, as stronger forcing will focus into
our southeast CWA and points east. There are also non-negligible
differences in the strength of the southern stream impulse, with
the ECMWF/EPS camp stronger and thus more aggressive in
spreading light rain/showers into a good chunk of the area.
Given the weaker forcing and drier posture of much of the non EC
guidance, kept PoPs in the 20-40% range (highest southeast of
I-55) and indicated sub mentionable (<15-20%) PoPs up in the
Rockford area. If and where rain does occur, a bulk of it would
likely occur in the overnight hours and thus less likely to
compromise outdoor plans.

In the wake of any lingering light rain/showers Saturday morning
over the eastern 1/3 to 1/2 or so of the CWA, expect dry
conditions the rest of the afternoon and early evening hours.
Temperatures will be a bit warmer, reaching primarily the low-
mid 70s away from Lake Michigan.

Saturday Night through Thursday:

Another modest short-wave impulse will move across the region
Saturday night into Sunday. Isolated to widely scattered showers
and maybe a few storms may drift eastward in tandem with the
wave into Sunday morning (~20-30% PoPs). Sunday afternoon, the
best chance for isolated to widely scattered renewed convective
initiation currently looks to focus primarily southeast of
I-55, closer to the departing short-wave. Even if/where any
thunderstorms develop, strong to severe storms are unlikely.
Temperatures will again step up some on Sunday away from the
lake, reaching the 75-80F range.

Summer-like warmth is forecast inland (highs in the lower to mid
80s) Memorial Day through midweek next week, while east to
southeast synoptic flow will be conducive to daily lake breezes
and cooler conditions lakeside. Some rain chances may return
midweek next week, though the progged pattern does not appear
supportive for organized convection, and there may be a play
for a bulk of the rain remaining south of our area.

Castro

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 612 PM CDT Thu May 21 2026

There are no key concerns for the 00Z TAF period.

NE winds at between 10 and 20 kt through mid-evening will ease
largely closer to 10 kt for the night, but with occasional gusts
as high as 20 kt. Expect NE winds between 10 and 20 kt during
the day on Friday.

A low potential for some spotty showers or sprinkles and
associated MVFR cigs exists Friday evening. Probabilities for
either are low enough through 06Z currently to omit a mention
in the 30-hr TAFs with MVFR becoming more likely during the
night.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement through Saturday afternoon for ILZ006-
     ILZ103-ILZ104.

IN...Beach Hazards Statement until 4 AM CDT Friday for INZ001-
     INZ002.

LM...Small Craft Advisory until 10 AM CDT Saturday for the IL
     nearshore waters.

     Small Craft Advisory until 4 AM CDT Friday for the IN
     nearshore waters.

&&

$$

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